As disclosed in, for example, JP-A-2007-155399, a conventional current sensor includes a sensor chip having a magnetoresistive element, a bias magnet located on both sides of the sensor chip, and a processing unit for calculating the magnitude of an electric current flowing through a current path based on a voltage generated by the sensor chip. A resistance of the magnetoresistive element changes according to a direction of a vector of a combined magnetic field of a magnetic field generated by the bias magnet and a magnetic field generated by the electric current flowing through the current path. The processing unit calculates the magnitude of the electric current based on the voltage generated by the magnetoresistive element.
In such a conventional current sensor, if there is a misalignment between the sensor chip and the bias magnet, an output voltage of the sensor chip has an offset. The offset reduces the accuracy with which the electric current is detected. Also, such an offset can occur due to the mismatch in resistance between the magnetoresistive elements of a bridge circuit and due to age deterioration of the sensor chip and the bias magnet.